Studies of interfacial regions by sum-frequency generation with a free-electron laser

The use of a Free-Electron Laser (FEL) allows the study of (non)linear optical properties of materials over unsurpassed large spectral intervals. As an example, we report on the use of a FEL as the infrared source in spectroscopic infrared-visible Sum-Frequency Generation (SFG). Employing the extremely wide tunability of the Free-Electron Laser for Infrared eXperiments (FELIX) at Rijnhuizen, we have studied the frequency dependence of the nonlinear susceptibility for sumfrequency generation in gallium phosphide between 20 and 32 m in great detail. We have developed a shortpulse visible laser system that is highly synchronous with FELIX thereby creating a two-color setup that can be broadly applied. Resonantly enhanced SFG in alphaquartz has been used to study the relative timing stability of FELIX and the synchronized picosecond-laser system.Paper presented at the 129th WE-Hearaeus-Seminar on Surface studies by Nonlinear Laser Spectroscopies, Kassel, Germany, May 30 to June 1, 1994     

Two-photon induced stimulated Raman scattering in cesium vapor

Two-photon induced stimulated Raman scattering has been observed for the first time. The observations have been made in cesium vapor. In the process cesium atoms are excited from the 6S_{$\text{3}\text{2}$} ground state to the 6P_{$\text{3}\text{2}$} excited state through the absorption of two laser photons at 1.064 μm and the emission of one scattered photon at 1.416 μm. The spectrum of the scattered light reveals the optical Stark shifts of the initial and final levels.     

Transmission reflection anomaly in second-harmonic generation from a monolayer

We show experimentally that in second-harmonic generation from a monolayer the radiation propagating in transmission and that in reflection can have very different magnitudes. The origin of this difference lies in destructive and constructive interference of the components of the nonlinear polarization that drive the field at the second-harmonic frequency.     

Giant enhancement of sum-frequency generation upon excitation of a surface plasmon-polariton

The generation of the sum frequency of visible (0.5235 μm) and IR (10 μm) radiation on smooth and corrugated silver surfaces is investigated. The sum-frequency signal obtained with a visible-range surface plasmon-polariton excited on a corrugated silver-air interface is found to be more than four orders of magnitude stronger than the signal from a smooth silver surface. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 9, 581–584 (10 November 1997)     

Performance measurement of sericin-coated silks during aging

Silks are among the most precious ancient and historic artefacts worldwide. While washing removes the natural gum from the fibres during the fabrication of most silk textiles, for a small proportion of historic silks some or perhaps all of the sericin still remains. This paper investigated the effect of sericin coating on the aging of silk fibroin by means of ATR and tensile testing. The results show that sericin can provide some extent of protection from light and heat aging. However, in high humidity envi...     

Enhancing the yield in surface sum-frequency generation by the use of surface polaritons

Received: 23 December 1998